[Scons-users] Make all Program and SharedLibrary targets implicitly Precious?
Andrew C. Morrow
andrew.c.morrow at gmail.com
Fri May 13 09:47:22 EDT 2016
Hi -
The equivalent of env.Append(LINKFLAGS=['-fuse-ld=gold']) is what MongoDB
uses to enable the gold linker:
https://github.com/mongodb/mongo/blob/d9a8e6a9db1bd48c2bbfb1ad18e7cb8e18eb7302/SConstruct#L2164-L2167
You almost certainly don't want to change LINK in a C++ build, for the
reasons you found. SCons is really fairly smart about how to invoke the
linker correctly (search for SmartLink).
Hope this helps,
Andrew
On Fri, May 13, 2016 at 4:56 AM, Ale Strooisma <
a.strooisma at student.utwente.nl> wrote:
> Ah okay, that works, thanks! Silly that I did not come up with that myself.
> Still a few more libraries to add, though. I'm definitely going to try
> your alternative.
>
> Kind regards,
> Ale Strooisma
>
> On 13 May 2016 at 10:44, Jörg Plate <patterner at gmail.com> wrote:
>
>> The stdc++ library tends to be in non-standard locations, since it's
>> depending on the compiler.
>> Try
>> locate "*libstdc++*so*"
>> and use the -L option with the correct directory. My g++ uses
>> /usr/lib/gcc/x86_64-linux-gnu/6/.
>>
>> Alternative: use g++ with "-Wl,-fuse-ld=gold" and let g++ deal with it.
>>
>> On Fri, May 13, 2016 at 10:30 AM, Ale Strooisma
>> <a.strooisma at student.utwente.nl> wrote:
>> > Andrew,
>> >
>> > inspired by this discussion I decided to try using gold as well. I ran
>> into
>> > a problem however, and can't seem to find a lot of documentation on
>> gold, so
>> > I hoped you could shed some light on this problem as you are working
>> with
>> > gold and scons.
>> >
>> > I changed to gold by adding LINK='ld.gold' to my environment object.
>> > However, now I get a lot of undefined reference errors during the
>> linking
>> > process - they all seem to come from the standard libraries. I interpret
>> > this as gold not linking those by default, so I added stdc++ to LIBS,
>> but
>> > that resulted in "ld.gold: error: cannot find -lstdc++".
>> >
>> > Any tips for getting this to work?
>> >
>> > Kind regards,
>> > Ale Strooisma
>> >
>> >
>> > On 13 May 2016 at 00:28, Bill Deegan <bill at baddogconsulting.com> wrote:
>> >>
>> >> Andrew,
>> >>
>> >> Looks reasonable.
>> >> What happens to the old binary if you os.remove it on one system, when
>> >> it's being used on another? (NFS)
>> >> Does it crash, or is the file kept alive via inode reference by running
>> >> process?
>> >>
>> >> -Bill
>> >>
>> >> On Thu, May 12, 2016 at 4:08 PM, Andrew C. Morrow
>> >> <andrew.c.morrow at gmail.com> wrote:
>> >>>
>> >>>
>> >>> OK, I got something that sort of works for incremental linking. I'm
>> sure
>> >>> it can be improved:
>> >>>
>> >>>
>> >>>
>> https://github.com/acmorrow/mongo/blob/0062b8bfa0c24812438f4765fa20755fb5f6fc54/site_scons/site_tools/incremental_link.py
>> >>>
>> >>> The binaries that ld.gold produces seem terribly broken, but perhaps
>> it
>> >>> will be useful on Windows.
>> >>>
>> >>> I wonder if .Precious should have a mode where it behaves like this by
>> >>> default, or if it should take an optional parameter. It seems useful.
>> >>>
>> >>> On Thu, May 12, 2016 at 12:18 PM, Andrew C. Morrow
>> >>> <andrew.c.morrow at gmail.com> wrote:
>> >>>>
>> >>>>
>> >>>> Hi Bill -
>> >>>>
>> >>>> I like this suggestion of adding a PreAction to each executable and
>> >>>> shared library, but I don't want to have to explicitly call
>> .AddPreAction on
>> >>>> each target.
>> >>>>
>> >>>> Can you suggest an easy way to achieve the same effect globally for
>> all
>> >>>> SharedLibrary and Program targets, without writing a PseudoBuilder?
>> I'm fine
>> >>>> though with reaching into the existing builders and altering them.
>> >>>>
>> >>>> Thanks,
>> >>>> Andrew
>> >>>>
>> >>>> On Sat, Apr 30, 2016 at 4:38 PM, Bill Deegan <
>> bill at baddogconsulting.com>
>> >>>> wrote:
>> >>>>>
>> >>>>> Andrew,
>> >>>>>
>> >>>>> How about a pre-action to mv the existing file to another name, and
>> >>>>> then copy it to original name, then incremental link the copy?
>> >>>>> That should resolve the crashing bit.
>> >>>>>
>> >>>>> lsof filename won't help if the files being used on another system,
>> but
>> >>>>> would if on current system. (to see if in use)
>> >>>>>
>> >>>>> -Bill
>> >>>>>
>> >>>>> On Sat, Apr 30, 2016 at 3:47 PM, Andrew C. Morrow
>> >>>>> <andrew.c.morrow at gmail.com> wrote:
>> >>>>>>
>> >>>>>>
>> >>>>>> Definitely a possibility. MongoDB probes for compiler support for
>> >>>>>> ld.gold and prefers it by default:
>> >>>>>>
>> >>>>>>
>> https://github.com/mongodb/mongo/blob/master/SConstruct#L2164-L2167
>> >>>>>>
>> >>>>>> The downside to using incremental linking and making dynamic
>> targets
>> >>>>>> Precious is that by overwriting the binaries you end up crashing
>> running
>> >>>>>> programs that have them mapped. That happens often enough during
>> developer
>> >>>>>> workflow that it is unfortunate.
>> >>>>>>
>> >>>>>> So, it definitely should be opt-in behavior, and a Tool sounds
>> right
>> >>>>>> for that.
>> >>>>>>
>> >>>>>> I also wonder whether such a Tool might be able to make intelligent
>> >>>>>> use of gold's --incremental-base file to avoid the above problem.
>> If you
>> >>>>>> first copied the dynamic target aside under a different name, then
>> unlinked
>> >>>>>> the original, then used --incremental-base pointing to the
>> moved-aside file,
>> >>>>>> perhaps you could avoid crashing programs that have the target
>> mapped. I'm
>> >>>>>> not sure though if the cost of the file copy would eat up most of
>> the gains
>> >>>>>> from incremental linking.
>> >>>>>>
>> >>>>>> That sounds complex enough to also warrant a separate Tool.
>> >>>>>>
>> >>>>>>
>> >>>>>> On Fri, Apr 29, 2016 at 1:52 PM, Bill Deegan
>> >>>>>> <bill at baddogconsulting.com> wrote:
>> >>>>>>>
>> >>>>>>> Andrew,
>> >>>>>>>
>> >>>>>>> Might make sense to make a gold linker tool?
>> >>>>>>>
>> >>>>>>> -Bill
>> >>>>>>>
>> >>>>>>> On Fri, Apr 29, 2016 at 9:47 AM, Andrew C. Morrow
>> >>>>>>> <andrew.c.morrow at gmail.com> wrote:
>> >>>>>>>>
>> >>>>>>>>
>> >>>>>>>> Thanks Bill -
>> >>>>>>>>
>> >>>>>>>> I think that sounds promising, I'll give it a look. If I get it
>> >>>>>>>> working well I'll ping the list back and describe my findings.
>> >>>>>>>>
>> >>>>>>>> Thanks,
>> >>>>>>>> Andrew
>> >>>>>>>>
>> >>>>>>>> On Fri, Apr 29, 2016 at 12:10 PM, Bill Deegan
>> >>>>>>>> <bill at baddogconsulting.com> wrote:
>> >>>>>>>>>
>> >>>>>>>>> Andrew,
>> >>>>>>>>>
>> >>>>>>>>> Likely you want to stick this logic in the emitter for building
>> >>>>>>>>> libraries and programs.
>> >>>>>>>>> SCons/Tool/link.py shlib_emitter() is the current logic.
>> >>>>>>>>> The environment tracks this in:
>> >>>>>>>>> env['SHLIBEMITTER'] which is a list.
>> >>>>>>>>> So if you append to SHLIBEMITTER and mark the relevant nodes
>> >>>>>>>>> Precious()
>> >>>>>>>>> env['PROGEMITTER'] is the emitter for programs. Looks like it's
>> >>>>>>>>> only defined for mslink and qt, so you can defined one on non
>> qt/mslink
>> >>>>>>>>> freely and do the same.
>> >>>>>>>>>
>> >>>>>>>>> Hope that helps
>> >>>>>>>>> -Bill
>> >>>>>>>>>
>> >>>>>>>>>
>> >>>>>>>>> On Fri, Apr 29, 2016 at 8:52 AM, William Blevins
>> >>>>>>>>> <wblevins001 at gmail.com> wrote:
>> >>>>>>>>>>
>> >>>>>>>>>> Andrew,
>> >>>>>>>>>>
>> >>>>>>>>>> I expect that you could make a Pseudo-Builder that wraps
>> Program
>> >>>>>>>>>> and Library calls, and replace the top-level calls with your
>> wrappers.
>> >>>>>>>>>>
>> >>>>>>>>>> I think you can replace them like env['BUILDERS']['xxxxxx'] =
>> >>>>>>>>>> Wrapper or env.AddMethod but I haven't tested this explicitly.
>> >>>>>>>>>>
>> >>>>>>>>>> https://bitbucket.org/scons/scons/wiki/ToolsForFools
>> >>>>>>>>>>
>> >>>>>>>>>> V/R,
>> >>>>>>>>>> William
>> >>>>>>>>>>
>> >>>>>>>>>> On Fri, Apr 29, 2016 at 4:21 PM, Andrew C. Morrow
>> >>>>>>>>>> <andrew.c.morrow at gmail.com> wrote:
>> >>>>>>>>>>>
>> >>>>>>>>>>>
>> >>>>>>>>>>> Hi -
>> >>>>>>>>>>>
>> >>>>>>>>>>> Is there a simple way to do this? I'd like to use ld.gold's
>> >>>>>>>>>>> incremental linking, but I don't want to need to add
>> .Precious to every
>> >>>>>>>>>>> executable and library in my project.
>> >>>>>>>>>>>
>> >>>>>>>>>>> Thanks,
>> >>>>>>>>>>> Andrew
>> >>>>>>>>>>>
>> >>>>>>>>>>>
>> >>>>>>>>>>> _______________________________________________
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>> >>>>>>>>>>>
>> >>>>>>>>>>
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>>
>> --
>> "I'm working on it."
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